Continuity: In the scene where Rob is walking on the street in the direction of Beth's apartment (just after leaving the electronics store), you see on the right-hand side of the street the orange framework of a store front. There are parked cars there, including a black Chevy Malibu followed by a white Mercedes, which Rob stands in front of as he points towards the military on the next block. Two scenes later they are (briefly) walking the opposite direction on the same street, which would be away from Beth's apartment. The orange framework is now on the left side and the direction of the parked vehicles is reversed. The black Malibu and white Mercedes are in different positions (as are the other cars on the street). I don't know New York City, so I don't know if the buildings in the background are different. Also, a man in a yellow shirt and tan pants runs past them in both scenes. It is the same man both times.

Continuity: When he's walking in the subway, Rob's shirt has a dark triangle of sweat (and dirt) on the back. In one clip the triangle is barely visible and the shirt looks a lot cleaner than before. In the next clip, the triangle is very clear again.

Factual error: In the first scene where the Army attacks the monster, the first tank that rolls by is actually a British FV-433 Abbot self-propelled gun made during the Vietnam war years, not an M109 Paladin which most people believe. (Paladin has a longer gun barrel, and has rear turret overhang.) And a few seconds later we see, next to the M1 Abrams, what appears to be an MLRS system firing, but is actually some kind of truck with a multiple rocket launcher, much like the Russian BM21, not the U.S. tracked MLRS system or the M1097 Avenger (which I originally thought it was).

Factual error: I just watched this film on DVD. I know this is a rule of the genre (see 28 Days/Weeks and Die Hard movies) but I find Beth's remarkable recovery from being speared with an iron bar - and stuck there for hours losing blood circulation and muscle cramping - to running around in Central Park helping Rob wholly unbelievable. Maybe she could limp down her building stairs, but whatever physical efforts she does afterwards are even more impossible than those of the monster.